1. Technical Field
The present invention relates to a resonator element, a resonator, an oscillator, and an electronic apparatus.
2. Related Art
In related art, it is known that, as a piezoelectric resonator element as an example of a resonator element is made smaller, the Q factor becomes smaller and vibration is hindered.
Specifically, in the piezoelectric resonator element, with elastic deformation due to flexing vibration, the temperature of the contracting surface rises and the temperature of the expanding surface falls, and a temperature difference is produced within. Thereby, in the piezoelectric resonator element, vibration called relaxation oscillation occurs in inverse proportion to a required time (relaxation time) until the temperature difference is eliminated (temperature equilibration) by thermal conduction (heat transfer).
As the piezoelectric resonator element is made smaller, the frequency of the relaxation oscillation and the frequency of the original flexing vibration come closer, and a phenomenon that the Q factor becomes smaller and the original flexing vibration is hindered occurs.
This phenomenon is called thermoelastic loss or thermoelastic effect, and, as measures therefor, in JP-UM-A-2-32229, a groove or a through hole is formed in the rectangular section of the piezoelectric resonator element to suppress the heat transfer from the contracting surface to the expanding surface, and thereby, reduction of the Q factor caused by thermoelastic loss is suppressed.
However, if a through hole is formed in the vibrating part (hereinafter, referred to as “resonating arm part”) of the piezoelectric resonator element as in JP-UM-A-2-32229, there is a problem that the stiffness of the resonating arm part is significantly reduced.
Further, if the piezoelectric resonator element is provided with an H-shaped groove (hereinafter, referred to as “groove part”) in the resonating arm part as in JP-UM-A-2-32229, the suppression of the heat transfer from the contracting surface to the expanding surface is insufficient and there is room for improvement in suppression of the reduction of the Q factor caused by thermoelastic loss.